Chattonella subsalsa

Chattonella subsalsa is a species of raphidophyte microalgae known for causing harmful algal blooms (HABs). While it is not a traditional plant pathogen, it acts as a significant biological agent affecting aquaculture productivity globally, primarily through its potent ichthyotoxic properties that cause severe damage to fish populations in marine environments.

The organism primarily affects fish kept in net-pen systems, such as salmon, sea bream, and other commercially important species. The cells release toxins and reactive oxygen species that irritate and destroy the epithelial tissues of the gills, directly hindering the fish’s ability to process oxygen and maintain ionic balance.

Key symptoms of the presence of this microalgae include the discoloration of water, often shifting towards reddish or brownish hues, and mass mortality events in fish farms. Affected fish exhibit extreme respiratory distress, excessive mucus production on the gills, and erratic swimming patterns before succumbing to asphyxiation.

The development and proliferation of Chattonella subsalsa are driven by specific environmental triggers, including increased water temperature and high nutrient loads (eutrophication). These conditions provide the ideal environment for rapid cell division, leading to high-density bloom events that can overwhelm the defensive capacities of aquatic animals within days.

Mitigation and control strategies are essential for sustainable aquaculture management. These include

• continuous monitoring and early warning systems based on water sampling;
• deployment of aeration systems to disrupt bloom layers;
• use of specialized gillnets or curtains to mitigate the spread of cells;
• management of feed inputs during peak bloom seasons to minimize metabolic stress on fish.